/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.camel.component.jms.reply;

import java.util.concurrent.ConcurrentSkipListSet;

import org.apache.camel.TimeoutMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.camel.TimeoutMap.Listener.Type.*;

/**
 * A creator which can build the JMS message selector query string to use with a shared reply-to queue, so we can select
 * the correct messages we expect as replies.
 */
public class MessageSelectorCreator {
    protected static final Logger LOG = LoggerFactory.getLogger(MessageSelectorCreator.class);
    protected final TimeoutMap<String, ?> timeoutMap;
    protected final ConcurrentSkipListSet<String> correlationIds;
    protected volatile boolean dirty = true;
    protected StringBuilder expression;
    private final Object lock = new Object();

    public MessageSelectorCreator(CorrelationTimeoutMap timeoutMap) {
        this.timeoutMap = timeoutMap;
        this.timeoutMap.addListener((type, cid, value) -> timeoutEvent(type, cid));
        // create local set of correlation ids, as its easier to keep track
        // using the listener so we can flag the dirty flag upon changes
        // must support concurrent access
        this.correlationIds = new ConcurrentSkipListSet<>();
    }

    public String get() {
        synchronized (lock) {
            if (!dirty) {
                return expression.toString();
            }

            expression = new StringBuilder("JMSCorrelationID='");

            if (correlationIds.isEmpty()) {
                // no id's so use a dummy to select nothing
                expression.append("CamelDummyJmsMessageSelector'");
            } else {
                boolean first = true;
                for (String value : correlationIds) {
                    if (!first) {
                        expression.append(" OR JMSCorrelationID='");
                    }
                    expression.append(value).append("'");
                    if (first) {
                        first = false;
                    }
                }
            }

            String answer = expression.toString();

            dirty = false;
            return answer;
        }
    }

    // Changes to live correlation-ids invalidate existing message selector
    private void timeoutEvent(TimeoutMap.Listener.Type type, String cid) {
        synchronized (lock) {
            if (type == Put) {
                correlationIds.add(cid);
            } else if (type == Remove || type == Evict) {
                correlationIds.remove(cid);
            }
            dirty = true;
        }
    }

}
